1. Field of the Invention
The present invention relates to a sheet stacking apparatus which stacks sheets, and more particularly, to a sheet stacking apparatus in which a discharge tray can be folded when a cover of an apparatus body is opened and closed, the discharge tray is extended when the cover is closed and the discharge tray is folded when the cover is opened, and the invention also relates to an image forming apparatus having the sheet stacking apparatus.
2. Description of the Related Art
Conventionally, there is an image forming apparatus which discharges recording sheets of paper (sheets) on which an image is formed in an apparatus body from the apparatus body, and the sheets are stacked on a discharge tray of the apparatus body. Examples of the image forming apparatus are a copying machine, a facsimile machine, a printer and a machine having multifunction of these machines.
As the discharge tray, there is a tray which can be extended if necessary when the recording sheet is of A3 size and long so that the sheet can be stacked and which can handle the long sheet. Such a tray is called an extension tray.
As an extension tray, there is a fixed-type tray which is merely formed into a plate-like shape and is fitted into and fixed to a portion of an exterior of the apparatus body if necessary. There is a turning type tray which is attached to the exterior of the apparatus body by means of a rotation shaft such that the tray can turn, and when the tray is not used, it is in intimate contact with the exterior and when the tray is used, the tray is separated from the exterior and is opened.
As a turning-type extension tray, there is an opening/closing type tray which forms a portion of the exterior and is used also as a cover of the apparatus body and in which the apparatus body is opened and closed. As the opening/closing type tray, there is an extension type tray which can further be pulled out if necessary and extended in a state where the apparatus body is opened (Japanese Patent Application Laid-open No. 2006-188363).
As the extension tray, there is a tray in which a maintenance cover which opens and closes the apparatus body when a cartridge in the apparatus body is to be exchanged or maintenance is to be performed is provided at a location where the cover is turned.
An image forming apparatus of recent years is required to save space for reducing the installation area or an occupying area. In the case of an upper portion of the exterior of the apparatus body is used also as the discharge tray, it is difficult to secure a length of the discharge tray which can stack the long sheet, because of a size limit of the apparatus body.
Generally, in the case of an image forming apparatus having a fixed-type extension tray, since the extension tray projects to a side of the apparatus body, it is necessary to increase a region (occupying region) of space occupied by the image forming apparatus.
In the case of the image forming apparatus having the turning-type extension tray, when the extension tray is opened, the extension tray projects from the side of the apparatus body. Therefore, it is necessary to secure a wide occupied region, and if the occupied region when the extension tray is opened is not taken into account, the extension tray can not be opened.
It is necessary that the image forming apparatus having the extension tray near the maintenance cover is disposed while taking the opening/closing amount of the extension tray, the moving amount of the extension tray and the opening/closing amount of the maintenance cover, and it is necessary to secure a wide occupied region.
It is an object of the present invention to provide a sheet stacking apparatus in which a discharge tray can be folded as a cover of the apparatus body is opened or closed, the discharge tray which can stack the long sheet is capable of installation, and a wide occupied region or a wide installation area is not required, and to provide an image forming apparatus having the sheet stacking apparatus.